Even if I am not a musician, this is really cool:
Direct Note Access heralds a whole new age in audio editing: for the first time in audio production history it is possible to edit individual notes within chords and polyphonic recordings – separately!
[Celemony]
That means, you can take any piece of music, e.g. from one of your music CDs, and change basically the melody of the song. This is a demonstration video:

